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Showing posts from January, 2015

How Spiders Get Bigger by Molting

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It had always been a mystery to me how arthropods manage to get bigger by shedding—or "molting"—their exoskeletons. If you're molting an exoskeleton, you're losing mass, right? It makes more sense that an arthropod would get smaller by molting. I've seen spiders before and after molting, but it wasn't until I witnessed a large spider molting that I finally understood what was going on. It turns out that I had seen the process before when a butterfly emerges from a chrysalis.

It is most apparent that a spider's legs get longer after molting. Here are two photos I took of a spider in 2011. Both photos are of the same spider, taken two days apart. The bottom photo is of the spider prior to molting, and the top is of the spider after molting. The measurements given are the lengths of the first legs. The two photos are proportioned correctly relative to each other, so you can visually compare the before and after sizes.


The spider is a male Mecaphesa dubia, wh…